CODEWITHSUNDEEP
assemblylittle-man-computer
Asher
Asher

Reputation: 1

Get maximum and count of input numbers

I need to create a simple LMC program for the following task:

Input a series of numbers and output:

  1. the largest among them, and
  2. how many numbers were entered.

The number 000 will be used to mark the end of the series of input numbers (000 is not considered as part of the series but it should be output if it is the only number entered).
Your program must work for ANY number of input values.

I think I need to use branching (BRZ, BRP, BR) but I'm not sure which type I'm supposed to use. Also, I've tried using an online LMC simulator but I'm not really sure where to start as LMC is very confusing.

How can I solve this?

Upvotes: -3

Views: 575

Answers (1)

Joshua
Joshua

Reputation: 43290

Answer given to question as updated by OP:

The question has been edited to be about branching. Branching is the core of learning assembly language. We can talk about that.

Fragment of data segment:

counter   DAT 0
max       DAT 0
current   DAT 0

Code to check if current is end of list:

         LDA current
         BRZ end
         ;... more code here

Simple. We check if current is currently zero and end the loop if it is. BRZ branches if the current value is zero.

Checking if current is the new maximum

         LDA current
         SUB max
         BRP positive
         BRA next
positive LDA current
         STA max
         BRA next     ;next is almost certainly back at top
end      HLT          ;the zero check ends up here
                      ;you probably need to insert OUT instructions

And here's a different branch. BRP branches if the value in current is not zero and the negative flag is not set. New concept flags. LMC has one flag, the negative flag. It is set if the previous operation underflowed/overflowed. If such an event happened we want set the value to the new maximum. Otherwise, we move on to the next value.

Answer given to question as original:

Apologies, I may have missread. I have interpreted it as given an array in memory terminated by zero, find the size and the largest. This problem is hard, and I understand why OP hasn't been able to post an attempt. This has to do with indirection. The only way to do indirection in LMC is self-modifying code.

First off, we have only two digits of indirection in the LOAD/STORE instructions, the total memory size is only 100 bytes, and we're going to need to make our program much smaller than that.

Starting with the data segment (which must go at the end):

one      DAT 1
ldazero  LDA 0
largest  DAT 0
count    DAT 0
first    DAT ?

Iterating over the list for the count.

ctr       LDA first
          BRZ  endcount
          LDA ctr
          ADD  one
          STO  ctr
          JMP  ctr
endcount  LDA  ctr
          SUB  ldazero
          STO  count
          HLT

Given the method ofindirection, it should be possible to write down how to do max. In order to avoid two counters, copy the value being compared into a working slot.

Upvotes: 1

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